1. Field of the Invention
The present invention relates to systems and methods for measuring volume and rate of fluid extraction from coal-seam gas wells, and the trending of volume and rate of fluid extraction from coal-seam gas wells by electrical means using differential pressure and metering with time integration. More specifically it relates to a methodology for automatically controlling variable speed submersible pumps in a coal-seam gas well to optimize both the water removal process and gas production from the wells. In addition, it relates to methods of remote trending data acquisition and remote event logging of fluid level, submersible pump speed, and submersible pump torque in a coal-seam gas well, and using the data to control and optimize production from the coal-seam gas well from a remote location.
2. Description of the Related Art
Coal-seam gas wells produce both hydrocarbon gases, primarily methane, and liquids, primarily water, herein referred to in combination as xe2x80x9cfluids.xe2x80x9d Referring to fry previous invention and claims, as set forth in U.S. Pat. No. 5,983,164, the method and apparatus for measuring and controlling the flow of natural gas from gas wells is taught. However, it neither teaches nor suggests the use of V-cone meters in such systems. In the past, the V-cone meter has been thought to be more suitable for measuring low volume gas of the type found in most coal-seam gas wells.
A typical coal-seam gas well has a low volume of gas production, for example less than 200 MCFD thousand cubic feet of methane gas and 200 Barrels of water per day per gas well. Gas is produced when water is removed from the coal-seam gas well bore. Therefore, removing or pumping out the water from the coal-seam gas well is the key aspect for the production of gas. In deep coal-seam gas wells, say below 7,000 feet, conventional beam-pumps are used to remove water from the coal-seam gas well. In less deep wells, submersible pumps are more practical and economical to use to remove water from the coal-seam gas well.
Coal-seam gas well liquid volume measurement devices are normally comprised of pulse train signal generating components, such as turbine meters with magnetic pick up, or positive displacement systems with a reed switch. The frequencies generated by such liquid volume measurement devices are generally believed to be linearly proportional to the liquid flow rate and volume passing through the meter. Electronic systems are common features of such state of the art liquid measurement system Such electronic systems are capable of counting the frequency generated by such meters, and may include firmware to accumulate or to total the number of pulses, and also to display the current flow rate and/or volume in a specific time interval, say daily, weekly, monthly, lifetime and so on. The electronic systems are also capable of scaling and processing the accumulated pulse data into volume units such as barrels or gallons. It should be further noted that the water produced from a coal-seam bed gas well, after being charcoal filtered or otherwise processed naturally, is suitable for human consumption or for agricultural uses, and is therefore, a valuable marketable product.
However, the state of the art liquid measurement systems only accumulate or provide total liquid volume measurements for a particular flow period, which data is then extrapolated into hourly, daily, weekly or monthly volume. The trending profile of the amount of actual liquid pumped in a given time period is not currently available, nor do the state of the art liquid measurement systems provide either auditable data or analytical trending data for the liquid which is produced
While analytical quality data or characterization in the above measurement systers is not an issue for accounting purposes, analytical quality data and characterization are vital information for control and optimization of a submersible pump used to remove liquid from a coal-seam gas well. In addition, as the water produced from a coal-seam gas well is a marketable product, analytical quality data and characterization can also be used to provides both records and an audit-trail for water custody transfer measurement. The state of the art systems are also capable of remote data acquisition of the accumulated daily, weekly or monthly volume of the water pumped. Instantaneous flow rate information is also available. This is similar to the prior art data acquisition capabilities for gas from gas well measurement systems, in which the state-of-the-art systems provide accounting data only.
In most coal-seam gas wells, submersible pumps with variable speed controllers are used as liquid removal systems. Removal of the liquid from a coal-seam gas well is required for release and recovery of the hydrocarbon gases, such as methane, absorbed in the liquid. However, removing liquid from a coal-seam gas well also lowers the hydrostatic head pressure of the liquid in the well. The state of the art systems do not provide analytical quality data for use in effectively controlling and producing gas and liquid from a coal seam well. With out interface software and systems to communicate with the variable speed controller of the pump, the-state-of-the-art system is incapable of fully automated operation for producing gas and liquid from a coal seam well. Therefore, manual operation and routine site visitation are a current state of the art necessity, and a costly part of a gas and liquid coal seam well operation. In the current state of heart strategic control of the pump run-time, the pump speeds, and the discharged pressure, has not been used to optimize the amount of gas and liquid produced from a coal-seam gas well, or to extend the life of the pump.
It would therefore be desirable to provide a method and system which provides analytical trending data of the liquid production and liquid level trending profile from a coal seam gas well. It would also be desirable to provide such a method and system which provides analytical trending data of the gas from a coal seam gas well. It would be further desirable to provide such a method and system that provides analytical trending data of both the gas and the liquids, i.e. the fluids from a coal seam gas well.
It is therefore an object of the present invention to provide a method and system which provides analytical trending data of the liquid production and liquid level trending profile of a coal seam gas well.
It is a further object of the present invention to provide such a method and system which also provides analytical trending data of gas from a coal seam gas well.
It is yet an additional object of the present invention to provide such a method and system that provides analytical trending data of both the gas and the liquid, i.e. the fluids, from a coal seam gas well.
Strategic control of submersible pump run-time, pump speeds, and the discharged pressure, will optimize the amount of gas and liquid produced from a coal seam gas well, and extends the life of the pump. To maintain and optimize gas production from a coal-seam gas well, the well must not be pumped dry or the liquid pump turned off when liquid is present in the well bore. Therefore, trending of the fluid level by means of reading the pressures at the bottom of the well and at the surface is critical information to control the pump. However, the pump must be shut-off if the liquid level falls-below a pre-set level and turned on when certain fluid level is allowed to build up. Therefore, the trending characterizations of the liquid and gas flow-rates as well as the fluctuation of the liquid levels with respect to time provide valuable diagnostic as well as auditable measurement data to optimize and control the operation of a coal seam well. The trending methodology creates high resolution trending profiles for liquid flow rates and liquid levels that represent the operating conditions of the submersible pump used as a prime liquid removal system for coal-seam gas wells. In the present invention, fuzzy logic or artificial intelligence control software based on characterization of liquid flow rates and liquid level profiles results in optimization of the gas produced. In addition, the methodology of the present invention enhances the resolution of the trending data and proper handling of power outages to the pump by time stamping all analog and digital events data.
To enhance the accuracy and quality of the trending data of liquid from a coal seam gas well, an improved method of data trending with a configurable variable-time-base is provided. Fuzzy logic or artificial intelligence control software is provided to effectively control the variable speed pump to enhance both liquid and gas production from the coal-seam gas well. The determination of remote trending of the liquid flow-rates provides a database for auditing and resolving custody-transfer measurement disputes of liquid removed from a coal seam gas well.
As noted above, common liquid measurement devices; turbine or positive displacement meters, generate pulse signals whose frequency is directly proportional to the velocity of the liquid flowing through the meter. The inclusion of trending the pulse train employs a simple logic of timing and counting the pulses for preset time intervals that can be downloaded as electrical signals to either an adjacent or a remote component. Each data point is time stamped before being storing in a circular buffer in the adjacent or remote component so that the trending data can be seamlessly retrieved and stored with unlimited time by the host component. The host component, which includes a data system, such as a simple desk top PC and, for example a portable note-book system, running state of the art software, such as Windows 95 or better, will display the trending data on a monitor, along with the event-log to effectively operate and optimize the production of gas and liquid fluids in an automated mode.
The existing trending system, as described in U.S. Pat. No. 5,983,164 is now improved to include a fixed time interval of digitally averaged data and data compression is employed during data transmission between the host and the remote components. To enhance and control the resolution of the data trend, the time interval of the averaged data point is configurable and downloadable from the host component system.
The Fuzzy logic or artificial intelligence control software of the present invention achieves optimum liquid production or removal process using a variable speed submergible pump. The key factor that affects the gas de-sorption process or release of the gas from the coal bed and liquid is to maintain an optimum flow of the liquid at a minimum fluid level. Test results have shown that most coal-seam gas wells there appears to be a co-relationship between the liquid removal rate and the optimum gas production. Therefore, the control software is designed to control the pump speed based on historical trends of liquid flow rate, gas flow differential pressure, pump torque, pump speed, liquid level, and line pressure within each well.
In order to allow remote control of submergible pumps within coal-seam gas wells, a vital liquid removal system, interface software and hardware are in operative communication with the pump controller via a newly developed serial data port. The software enables the remote component to monitor and log the operating status of the pump and trend the operating parameters such as pump speed, running torque, and operating current. Menus which are taught and detailed below allow an operator to remotely download control strategy changes, such as pump speed changes, torque limit and fluid level zones to shut down pump, and time delay with fluid level build-up to restart pump. By leaming the operating trend of the pump and the production characteristic of the coal-seam gas well artificial intelligence to properly control the pump may be developed. The present invention, in conjunction with the gas measurement and control taught by U.S. Pat. No. 5,983,164 allow complete automation of the gas and liquid production from a coal-seam gas well.
The availability of pump trending or diagnostic data, and the ability for an adjacent or remote component to communicate with thee submersible pump controller allows operation of the coal-seams gas field from the office or where a conventional or cell phone service is available. Significant savings of manpower and vehicle cost are realized by operating in a fully automated mode.
These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description and accompanying drawings, shown the contemplated novel construction, combination, and elements as herein described, and more particularly defined by the appended claims, it being understood that changes in the precise embodiments to the herein disclosed invention are meant to be included as coming within the scope of the claims, except insofar as they may be precluded by the prior art.